The present invention relates to (a) methods for modifying the gelation time of organically crosslinked, aqueous gels, (b) gels formed by the foregoing methods, (c) compositions for forming the gels, and (d) subterranean formations containing the gels.
Gels are used for several purposes in connection with the production of a natural resource (e.g., oil, natural gas, and geothermal fluids) from subterranean formations. For example, gels are employed (a) to reduce the water/natural gas production ratio, (b) to reduce the water/oil production ratio, (c) to plug off water producing zones within a subterranean formation, and (d) to conform the fluid permeability across the face of a subterranean formation.
In addition, gels can be used to contain migrating, hazardous wastes in the subsurface.
An important factor in forming these gels is the time it takes for a gelable, polymer-containing composition to gel. In some environments (e.g., low temperature oil-producing reservoirs), the gelation time is too long, requiring extended shut in periods to allow complete gelation of the composition and to prevent the flow of uncrosslinked polymer back into a wellbore.
In other environments, the gelation time is too short. In this latter case, the rapid formation of the gel impedes the satisfactory distribution of the gelable composition prior to gelation.
Accordingly, there is a need to modify the gelation time of a gelable composition in order to form a gel in a satisfactory time frame.